Poly(ethylene terephthalate) (PET) can be injection molded into electrical conductors that can withstand rigorous thermal, mechanical, and chemical exposure. However, the crystalline nature of PET results in anisotropic shrinkage which causes warpage, particularly in long (i.e., greater than about 8 inches) connector designs.
Polysulfone, because of its amorphous nature, can be molded virtually warp-free. However, it is prone to chemical attack. Further, due to relatively high moisture absorption and a glass transition temperature of only about 374.degree. F., polysulfone cannot be used to make connectors that will be subjected to vapor phase reflow and infrared reflow applications, such as vapor phase soldering conditions (419.degree.-425.degree. F.) during assembly operations.
Blends of polysulfone and PET combine the best properties of each component and have been used to make warp-resistant connectors that have sufficient chemical resistance to withstand cleaning operations normally used in the electrical/electronic industry. The increased interest in the vapor phase soldering of components surface mounted on printed wiring boards has revealed a shortcoming of said blends of polysulfone and PET. The shortcoming manifests itself as blisters that develop on molded connectors when they are subjected to vapor phase reflow and infrared reflow conditions after exposure to ambient or humid conditions.